1. Field of the Invention
The present invention is directed to a method and apparatus for controlling the movement of web of material being fed at a constant rate of feed through a web take-up device to a machine which acts on a portion of the web as that portion is at a standstill. The web take-up device includes a pair of members mounted in a side frame for rotation on a first axis, a roller for engaging a portion of the web, and means for mounting the roller on the pair of members for rotation on a second axis which is offset or eccentric to the first axis with the amount of offset or eccentricity being controlled by a control screw.
2. Prior Art
In one known method and apparatus for forming blanks utilizing a platen press, a web of material, for example cardboard, is generally delivered to the platen press in a continuous manner. In view of the fact that the platen press is able to die cut a portion of the web if this portion is temporarily stopped or at a standstill, continuous feeding of the web causes the web to accummulate in front of the cutting station or the platen press. To overcome this problem of accummulation of the continuously moving web, several solutions have been suggested and tried out.
The most simple solution consists of forming a loop in the web prior to its introduction into the press. However, fluttering will occur in the loop and this solution has been found to be unsatisfactory when the production speed is increased and when the accuracy of the position of the web portion introduced into the platen press must be maintained in order to obtain a registry between the printing on the web and the die cut pattern.
Machine builders, therefore, imagined a way to check the formation of the web loop in such a way that the effect of fluttering on the web would be reduced to a very minimum at a point of entry to the machine by using a loop control device. For this purpose, an appliance was used which involved the web being lead around a circumferential portion of a roller which is mounted between two rotating members or plates with the axis of the roller being offset from the axis of rotation of the plates. German Pat. No. 1,061,167 of July 6, 1957 is an example of this type of apparatus.
However, the above-mentioned solution did not bring about the necessary improvements in controlling the movement of the web and a third solution was directed to a complete and permanent web loop control device or apparatus. This apparatus generally includes an infeed and pull rollers moving the web up to an inlet of a cutting station and an appropriate appliance or device for providing an interlock on the web is arranged at the inlet of the cutting station. The web track between the pull rollers and interlocking devices is equipped with a compensator controlled by means of a cam and designed to continuously maintain the loop of the web under adequate tension. This compensator, which consists of a half cylinder on which the web slides around, is shifted by means of a lever controlled by a pull rod which is itself connected to a cam and cam lever assembly. However, since an alternative motion to actuate the compensator will put the mechanical components under a rather severe stress and strain, which are dependent on the operating speed desired, this design has many limitations. In addition, the device of the third suggested solution compulsorily requires the use of an appliance or device for interlocking the web at the moment when the platen press is actually being closed.